Many wireless power transmitters strive to provide an even magnetic field to all chargeable devices, such that all devices may receive a similar amount of power (e.g., a similar voltage is induced in the receive coils of all devices). However, there may be certain circumstances in which the magnetic field should be adjusted to provide more or less power to a particular device. In addition, it may also be useful to detect where a chargeable device is located on a transmitter pad, and which coils to energize for charging. This may reduce wasted power as well as unwanted magnetic field emissions. Furthermore, it may be useful to be able to adjust the efficiency and power handling of the wireless power transfer system. Accordingly, methods and apparatus for wireless power transfer utilizing transmit coils driven by phase-shifted currents are desirable.